An interventional operation is a developed method of modern surgery, the difference of the interventional operation from the traditional surgery lies in that no surgical operation is needed, a special surgical instrument, such as a catheter, a frozen needle, a radio frequency ablation needle, a guide wire and the like can be penetrated into a focus location or a surgical target location in vivo through a very small wound, and then a treatment purpose is achieved by a variety of physical/chemical effects, so as to solve the problems of tumor excision, biopsy, artificial equipment placement and the like that can be solved only by open surgery previously.
In an interventional operation process, a doctor cannot directly observe a treatment site or focus in a patent body and need to rely on computer-assisted surgery navigation technology guided by medical images. The computer-assisted surgery navigation technology is a cross research topic integrating computer science, artificial intelligence, automatic control, image processing, three-dimensional graphics, virtual reality and clinical treatment and other aspects. Multiple modes of medical images are adopted in the surgery navigation technology to assist the doctor to directly penetrate the surgical instrument into the focus for local treatment, so as to improve the surgery quality, reduce surgical trauma and reduce the pain of patients.
Surgical navigation is used for guiding the execution of clinical surgery in real time by means of a medical image of the patient and a three-dimensional model generated thorough reconstruction of the medical image. The medical image data of the patient are obtained, for example, by means of CT (computerized tomography) or MM (Magnetic Resonance Imaging) scanning. A surgical navigation system associates the preoperative medical image data with the intraoperative surgical site of the patient through a positioning device, and can accurately display an anatomical structure of the patient and the details of a three-dimensional spatial position near the focus in a software interface. When the surgical instrument points to any location in the patient body, the coordinate information thereof will be obtained by the navigation system in real time and is displayed on the three-dimensional model of the patient. In this case, even if no surgery under a operation knife is carried out on the patient, the doctor can get the relative position relation of the surgical instrument and the tumor focus in real time.
Compared with the traditional surgical means, the surgical navigation has the following advantages:
1, the focus can be reconstructed in real time through the three-dimensional technology, and the structural features on the surrounding of a surgical field are displayed;
2, the most suitable surgical approach can be selected through a preoperative surgical plan design;
3, possible encountering tissue structures on the surgical approach can be displayed;
4, important tissue structures that should be evaded, for example, blood vessels, nerves, bones and the like can be displayed;
5, a range for treatment of the focus can be displayed;
6, the position and orientation of the surgical instrument can be accurately calculated and displayed in real time;
7, the spatial position relation of the surgical instrument and the focus can be displayed, and the advance direction of the surgical instrument can be indicated; and
8, the surgical approach can be adjusted in the surgery in real time so as to arrive at the focus location more accurately.
For the convenience of description, a CT image is used as an example of the medical image below, but obviously other images, such as an MM image, can also be used as the example of the medical image.
Real-time surgical navigation relates to the use of a positioning device or a tracking system, for example, an electromagnetic (EM, electromagnetic) tracker is used for tracking the distal tip of a surgical tool, such as a puncture needle, so as to associate the position of the surgical tool with the preoperative medical image, for example, the CT image and display a fused image to a clinician. To achieve data integration between a CT space and a tracker space, a registration process based on reference marks is generally carried out before navigation. These reference marks (external reference marks or internal anatomical reference marks) are identified from the CT image, and these reference markers are touched by a calibrated tracking probe to obtain coordinates of these reference markers in the tracker space, which is called a positioning coordinate system below. Thereafter, registration based on points is executed to find a coordinate transformation matrix between the CT space and the tracker space. A registration matrix is obtained through the coordinate transformation matrix, and the registration matrix is used for aligning the surgical tool with the preoperative medical image, so that the image of the surgical tool can be accurately fused with the CT image in a CT coordinate system based on the position information of the surgical tool in the positioning system, and the fused image is visually displayed to the clinician.